Cathode-ray tube and method of manufacturing such tubes



April 1, 1952 J DE GIER 259L521 CA DE-R'AY TUBE. AND METHOD BES OF NU TURING SUCH TU Fil March 7, 1950 V INVENTOR. x 1 JOH/WES or 6/02 HGBVT l atented Apr. l, 1952 .CATHODE-RAY TUBE AND METHOD OF MANUFACTURING SUCH TUBES Johannes de Gier, Eindhoven, Netherlands, as: signor to Hartford National Bank and Trust Company, Hartford, Conn, as trustee Application March 7, 1950, Serial No. 148,032 In the Netherlands March 30, 1949 1 Claim.

Cathode-ray tubes for television reception are generally mounted in a cabinet. With tubes arranged in a horizontal position, their length is a measure of the depth of the apparatus and also of the other dimensions which vary with the depth to a greater or less degree for aesthetic reasons. Consequently, in order to minimize the size of the apparatus it is of importance to reduce the length of the cathode-ray tube as much as possible.

The present invention relates to cathode ray tubes comprising a cylindrical part and a substantially conical part. The length of the cylindrical neck of the tube is determined by the space occupied by the electrode-system for producing the electron beam and by the length of the coil producing the magnetic focussing field. With magnetic deflection, as is generally utilized for television reception, the deflection coils gnay also influence the length of the neck. There is no reason for making this part of the tube longer than is required by the said factors.

The length of the conical part of the tube is related to the desired deflection sensitivity, which varies in direct proportion with the spacing between the deflection system and the collecting screen for the electron-beam. When reducing this length, the beam deflection increases and theenergy for producing the deflecting fields increases. This limitation may be obviated by extending the range in'which the deflecting fields operate and which is traversed by the beam.

It is not invariably possible to give the magnet coils used in television-reception for producing the deflecting fields the optimum length with a view to reducing the energy. The geometric relation existing between the, coil length and the diameter of the tube determines the extreme position in which the beam is deflected without being intercepted by the neck. Consequently, lengthening of the deflection range is not possible, since the area of image of the collecting screen is no longer entirely covered. In this event, the corners of a rectangular area of image are cut off, which, of course, is not permissible.

This disadvantage has already been experienced. In order to obviate it, cathode-ray tubes for television reception are sometimes provided with a conical part, the sectional area of which is rectangular, so that it has the shape of a truncated pyramid. The sectional area of the tube where the neck adjoins the cone is then a reduced projection of the area of the image on the fluorescent screen.

A glass bulb of rectangular section can be moulded. The cylindrical neck and the conical part are made separately and then the neck is sealed to the narrow end of the conical part. Since I am concerned with a junction between two parts, one of which has a circular and the other a rectangular section, this operation is more complicated than a joint between two parts having similar sections. However, it is advisable not to establish the joint at the transition between the cylindrical part and the conical part. Therefore, with tubes of which the conical part has a section having rotational symmetry a short cylindrical portion is sometimes pressed on to the cone so that the seal may be spaced apart from the transition between neck and cone.

The invention combines the advantages of a rectangular section, having regard to reducing the length of the tube, and those obtained by the last-mentioned step.

The cathode-ray tube to which the invention. relates comprises a glass vessel which encloses the exhausted space in which are housed the electrodes producing and directioning the electronbeam and the fluorescent screen, the said vessel consisting of a cylindrical neck and an adjoining substantially conical part.

According to the invention, the tube has a rectangular internal section and a circular external section at the transition of the conical and the cylindrical part.

The internal section of the mould which may be used for making the wall of the tube has rotational symmetry so that manufacture of the mould is easy. At the-narrow end, the conical part may develop into a cylindrical aperture. The manufacture of a corresponding die member which is rectangular at the transition between the conical and the cylindrical part, does not involve difiiculties. The area where the neck develops into the cone is mechanically, the weakest part of the tube. The wall thickness in situ should be such that the tube has sufficient rigidity to permit its further working, for example sealing of the neck and securing and sealing of the electrodes. In the existing constructions the thickness of the wall must therefore not be smaller than that of the remaining part of the cone which is required to Withstand the pressure of the air, although a smaller wall thickness at the said area would permit a greater size of the space in which the beam travels. At the corners of the internal rectangle in the tube there is no objection to make the wall thinner, since the required mechanical strength is retained owing to the greater wall thickness along the straight sides of the section. This results in a further reduction of the length of the tube with the same surface area required for the beam.

In order that the invention may be readily carried into efiect, one example will now be described in detail with reference to the accompanying drawings.

The accompanying drawings show the difierence between a glass tube of rectangular section and the shape obtained according to the invention. The right-hand part of Fig. l rel-ates to the known shape of tube, while the left-hand part shows the new shape. These two parts are sectional views taken on the line A-B- of Figs. 2 and 3 which are longitudinal sectional views.

Fig. 4 is a sectional view taken on the line C--D in Fig. 1. In these figures, the right-hand part likewise relates to the known shape and the left-hand part to that obtained according to the present invention.

The tube wall has a cylindrical part I conical part 2. At the top the cone has a rectangularinter'nal section,whence the curved lines -3 at the transition between the conical part 2 and the cylindrical neck portion. The point of maximum permissible deflection of the cathoderay "beam travels along these lines in scanning the area of image. In the construction shown in -;the right-hand half of the figures, the wall thickness is the same throughout, in contradistinction to the construction shown in the lefthand half. From Fig. 1 it appears that 'in the sectional plane AB the wall thickness along the straight sides is considerably greater, whereas at the corners of the rectangular internal sec tion the wa ll may be thinner. This likewise appears-from Figss2, S and 4. This is'not harmful to the strength of the tube since, owing to the greater wall thickness on the straight sides, the

weakening at the corners is sufiiciently compensated.

the mold is a die H whose contour corresponds to the internal configuration oi the tube and which fits into the mold with sufiicient clearance to permit the tube material to be poured therebetween, thus forming the tube.

As will be seen from Figs. 6 and '7, the die has a rectangular cross-section at the juncture of the flared out conical portion and the cylindrical portion of the tube element, while in the cylindrical portion as well as in the conical portion, the internal cross-section as determined by the die is circular.

What I claim is:

In a cathode-ray tube for television reception, a vitreous envelope therefor comprising a conical portion flaring outwardly for supporting a screen at one end thereof and an adjoining cylindrical portion for housing an electron gun, said envelope having an internal section which is circular in the cylindrical portion and rectangular in the conical portion and having an internal section which changes from a circular section to a rectangular section in a continuous transition at the juncture of the conical and cylindrical portions of the envelope, the external section at said juncture maintaining a circularsection in a continuous transition to a larger diameter from the cylindrical porticirto the conical portion of the envelope, the wall thickness at the corners of the rectangular cross section being relatively thinner than the wall thickness of the cylindrical portion of the ,tube having internal and external rotational symmetry.

JOHANNES DE GIER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,117,019 Bowie Oct. 3, 1939 2,178,826 Bowie Nov."7, 1939 2,232,098 Deichman Feb. 18, 1941 FOREIGN PATENTS Number Country Date 525,181 Great Britain Aug..22,;l9.40 867,824 France -Sept. 1,1941 589,135 Great Britain J une:1.2,:19,47 

